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Flashfire opal is a rare variety of precious opal exhibiting intense, dynamic play-of-color with dominant red-to-orange flashes that appear to move rapidly across the stone’s surface when viewed from different angles. The phenomenon occurs due to the unique internal structure of uniformly arranged silica spheres that diffract light.
This distinctive gem forms in volcanic regions where hydrothermal fluids deposit silica gel in cavities and fissures. The most notable deposits are found in Mexico’s Queretaro mines, where the opals develop under specific geological conditions involving rapid cooling of silica-rich solutions. The stones display exceptional brightness and contrast, with color patterns that can shift dramatically from deep reds to electric oranges and occasional blues.
The term “”flashfire”” refers to the swift, flame-like movement of color across the stone’s surface, created by the precise spacing of silica spheres approximately 0.2 microns in diameter. These opals typically contain 6-10% water content and register 5.5-6.5 on the Mohs hardness scale.
Flashfire Opal is typically a natural gemstone.
Common names for Flashfire Opal include Fire Opal, Girasol Opal, and Sun Opal.
Flashfire opal, like other opals, has a relatively low Mohs hardness rating, typically ranging from 5.5 to 6.5. This makes it somewhat susceptible to scratches and abrasion.
The refractive index of flashfire opal generally ranges from 1.37 to 1.52. This variation contributes to the stone’s distinctive play of color.
Flashfire opal exhibits a subvitreous to waxy luster, which enhances its visual appeal and is a key characteristic that contributes to its desirability.
Opals, including flashfire opal, do not have a defined cleavage plane. They are generally amorphous, meaning they lack a well-defined structure that would facilitate cleavage.
This type of opal typically displays a conchoidal fracture, which is smooth and curved, similar to the fracture surfaces seen in glass.
The specific gravity for flashfire opal can range between approximately 2.15 and 2.21, which is considered typical for opals.
Opals, such as flashfire opal, are isotropic gems and do not exhibit double refraction. They have a single refractive index.
Flashfire opal is well-known for its remarkable play of color or “”fire,”” which is caused by the diffraction of light passing through its silica sphere structure, rather than dispersion as seen in diamonds.
Flashfire opal is amorphous, meaning it does not have a crystalline structure. This is characteristic of all types of opal.
The base color of flashfire opal can vary widely and includes white, gray, red, orange, yellow, green, blue, and brown. The unique appeal of flashfire opal lies in its vibrant flashes of iridescent colors across the spectrum.
Flashfire opals range from opaque to translucent, which affects how the color play is perceived and the depth of color visible within the stone.
This gemstone does not exhibit pleochroism due to its amorphous nature and isotropic properties.
Flashfire opal can show fluorescence under ultraviolet light, typically displaying a green or white glow, which varies depending on the individual stone’s characteristics.
Opals, including flashfire opals, have fair to poor toughness due to their high water content and internal structure, making them sensitive to being dried out, heated, or stressed.
Flashfire opal is generally brittle, making it more susceptible to damage from impact and pressure.
Being isotropic, flashfire opal has no optic sign as it does not doubly refract light.
Flashfire opal does not typically display a characteristic absorption spectrum but is admired for its play of color caused by light interference.
Opals are composed of silicon dioxide (SiO2) and water. Flashfire opal contains between 6% to 10% water by weight.
While not common, some flashfire opals can exhibit a cat’s eye effect if they possess aligned fibrous inclusions or internal structures.
Asterism, or the star effect, is generally not observed in flashfire opals.
The iridescence, or play of colors, in flashfire opal is one of its most defining and attractive features, resulting from the interference and diffraction of light.
Flashfire opal is not magnetic.
Being composed mostly of silicon dioxide, flashfire opal has poor electrical conductivity.
Flashfire opal is not radioactive.
